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麻烦的Python操作/循环顺序(Trouble with Python order of operations/loop)

 我有一些代码用于将CSV文件转换为制表符分隔文件。 我的问题是我无法弄清楚如何以正确的顺序写出正确的值。 这是我的代码：  
for file in import_dir:
    data = csv.reader(open(file))
    fields = data.next()
    new_file = export_dir+os.path.basename(file)
    tab_file = open(export_dir+os.path.basename(file), 'a+')
    for row in data:
        items = zip(fields, row)
        item = {}
        for (name, value) in items:
            item[name] = value.strip()
    tab_file.write(item['name']+'\t'+item['order_num']...)
    tab_file.write('\n'+item['amt_due']+'\t'+item['due_date']...)
 
 现在，由于我的两个write语句都在for row in data循环中的for row in data ，因此我的头文件被多次写入。 

 如果我突然出现第一个write语句，我将会出现明显的格式错误。 
 如果我将第二个write语句移到第一个然后突出的上面，我的数据就会出现故障。 

 我该怎么做才能确保第一个write语句作为标题写入一次，第二个写入为CSV文件中的每一行写入？ 如何在不破坏字典的情况下在循环外提取第一个'write'语句？ 谢谢！ 

I have some code that is meant to convert CSV files into tab delimited files. My problem is that I cannot figure out how to write the correct values in the correct order. Here is my code: 
for file in import_dir:
    data = csv.reader(open(file))
    fields = data.next()
    new_file = export_dir+os.path.basename(file)
    tab_file = open(export_dir+os.path.basename(file), 'a+')
    for row in data:
        items = zip(fields, row)
        item = {}
        for (name, value) in items:
            item[name] = value.strip()
    tab_file.write(item['name']+'\t'+item['order_num']...)
    tab_file.write('\n'+item['amt_due']+'\t'+item['due_date']...)
 
Now, since both my write statements are in the for row in data loop, my headers are being written multiple times over. 

If I outdent the first write statement, I'll have an obvious formatting error. 
If I move the second write statement above the first and then outdent, my data will be out of order.

 What can I do to make sure that the first write statement gets written once as a header, and the second gets written for each line in the CSV file? How do I extract the first 'write' statement outside of the loop without breaking the dictionary? Thanks!

原文：https://stackoverflow.com/questions/16845878

更新时间：2021-10-20 17:10

最满意答案

 您可以使用setInterval方法在每个固定时间延迟上调用函数，在大多数情况下，它将与clearInterval方法一起用于停止重复调用，这里是一个示例：  
var interval = setInterval( function () {
    afoo( function (err) {
        // clear interval if an error occured
        if ( err ) {
            console.log(err);
            clearInterval(interval);
        }
    });
}, 5 * 60 * 1000);
 
 如果你想要更多的控制，那么使用node-cron模块，它与linux系统使用的cron模式相同，例如：  
const CronJob = require('cron').CronJob;

// run afoo function every 15 min
var job = new CronJob('00 15 * * * *', afoo);

You could use setInterval method to call a function on every fixed time delay, in the most case it's used in conjunction with clearInterval method to stop the repeated calls, here is an example: 
var interval = setInterval( function () {
    afoo( function (err) {
        // clear interval if an error occured
        if ( err ) {
            console.log(err);
            clearInterval(interval);
        }
    });
}, 5 * 60 * 1000);
 
If you want more control then use node-cron module, it has the same cron pattern used by linux systems, Example: 
const CronJob = require('cron').CronJob;

// run afoo function every 15 min
var job = new CronJob('00 15 * * * *', afoo);

麻烦的Python操作/循环顺序(Trouble with Python order of operations/loop)

最满意答案

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